The Arizona Cardinals head into the 2015 season with numerous questions on the offensive side of the football.

Carson Palmer's health, Larry Fitzgerald's age, and the incredibly poor offensive line play that the team endured last season are a few of the story-lines that fantasy owners are tracking this offseason.

Make no mistake, Bruce Arians and the Cardinals coaching staff did not ignore the running game this offseason. With their first round pick in the 2015 NFL Draft, the Cardinals selected offensive tackle D.J. Humphries from Florida. In the third round, they selected Northern Iowa running back David Johnson.

Did the Cards draft Johnson to replace incumbent Andre Ellington?

Last month, Cardinals head coach Bruce Arians said that Ellington will have his same role, but with his injury history and the team's investment of a third round pick, Johnson appears to be a sleeper worth reaching for on draft day.

Who Is David Johnson?

The Arizona Cardinals have often referred to Johnson as Andre Ellington 2.0. I see Johnson as much more than an Ellington carbon-copy.

First of all, Johnson is 6'1" and 224 pounds. Ellington is much slighter at 5'9" and 199 pounds. Johnson's size profile compares near exactly to the Steelers' Le'Veon Bell.

Johnson started his career at Northern Iowa as a wide receiver. Not surprisingly, reports out of Cardinals camp say that Johnson is a natural pass catcher out of the backfield.

Johnson had 38 receptions in both his junior and senior year and caught at least 32 in each of his four years in college. In 2014, he posted an impressive 14.1 yards per catch average on those receptions.

Scouting reports on Johnson mention that he has excellent footwork and body control, even with his taller than normal 6'1" frame. His college game tape reveals that he often uses quick jump cuts and lateral moves to slice through defenses. Johnson is effective running both inside and outside, shown by his four year 5.4 yards per carry average at Northern Iowa.

According to Player Profiler, Johnson's College Dominator score was 40.8%. The College Dominator score is a metric that takes into account the total yards and touchdowns that a player produces for his team. Anything above 40% is considered excellent.

Coach Arians has praised Johnson's play through mini-camp. However, Arians has indicated that Ellington will remain the starter. The question is now whether both Cardinals backs can carve out a fantasy relevant role this season.

Is Ellington Really the Cardinals' Guy?

The Cardinals' running game was nothing short of horrendous in 2014. When Carson Palmer went down with injury, defenses were able to stack the box against the historically inept Arizona replacement quarterbacks.

Looking at Arizona's 2014 season with our Toby Gerhart (-14.00) and Darren McFadden (-22.48), just to put this in context.

For a guy who had 201 carries, it is hard to believe that he performed that poorly. Sure, some blame goes to the porous offensive line, but Ellington was just terrible as a rusher last season.

For a historical perspective, among rushers with 50 or more carries in a single season, Ellington had the fifth worst rushing season the Cardinals have had since 2000.

I don't think David Johnson is going to be sitting on the bench as a nice shiny toy in Arians' offensive arsenal.

Run Game Outlook in 2015

The Cardinals clearly have made a concerted effort to improve the run game this offseason.

Additions along the offensive line, including free agent Mike Iupati, will drastically improve the ability for the Arizona running backs to find space out of the backfield.

Arians does not just hand the keys to young players. An ideal situation for rookie Johnson in 2015 is for him to perform so well in camp that he carves out a role early in the year to build upon as the season wears on.

Looking at current average draft position (ADP) Johnson is hands down the better bargain in the Arizona backfield. According to Fantasy Football Calculator, Ellington is being taken at pick 4.10 while Johnson is being taken five full rounds later at pick 9.10.

The word is getting out on Johnson, and he will certainly continue to trend upward if he performs well in the preseason. Keep an eye on his ADP, as it has crept up four full rounds since June 1st. Right now he is still a great value to target as your fourth running back.

For my money, David Johnson is the Cardinals running back I am gambling on in 2015